CODEWITHSUNDEEP
c++c++11wchar-t
golobitch
golobitch

Reputation: 1334

Content of wchar is deleted

I have this code:

JSONObject object;
if (value->IsObject())
{
    object = value->AsObject();
    const wchar_t *tmp = from_string(entity_id);
    std::wcout << tmp << std::endl;
    std::wcout.flush();
    if (object.find(tmp) != object.end())
    {
        std::wcout << tmp << std::endl;
        std::wcout.flush();
        initFromJSON(object[tmp]->AsObject());
    }
    else
    {
        return false;
    }

}

Problem here is that after inner if statement, the content of a tmp is empty. Before that it's not. When I try debuggin, it's everything ok, the content is not deleted. But when I run program, content is deleted. Any idea why?

Method from_string(entity_id) only convert from string to wchar like this:

std::wstring result;
for (int i = 0; i<content.length(); i++)
    result += wchar_t(content[i]);
return result.c_str();

Methods JSONObject::find(...) and JSONObject::end() are this:

iterator find(const key_type& __k)             {return __tree_.find(__k);}
iterator end() _NOEXCEPT {return __tree_.end();}

I don't believe that is problem in find(...) or in end(). I'm guessing that problem is somewhere else but I cannot locate it. Because the content of wchar is empty after the if statement I cannot say

initFromJSON(object[tmp]->AsObject());

because object[tmp] doesn't exist.

Any advice what am I doing wrong?

Upvotes: 0

Views: 86

Answers (1)

PaulMcKenzie
PaulMcKenzie

Reputation: 35440

The issue is that your from_string function returns a pointer to a local entity, namely the return value of std::wstring::c_str(). Thus you've introduced undefined behavior.

I see no reason at all for the tmp variable being a pointer. You should be able to do something like this instead:

std::wstring from_entity(...)
{
    std::wstring result;
    for (int i = 0; i<content.length(); i++)
        result += wchar_t(content[i]);
    return result;
}

And then this:

JSONObject object;
if (value->IsObject())
{
    object = value->AsObject();
    std::wstring tmp = from_string(entity_id);
    std::wcout << tmp << std::endl;
    std::wcout.flush();
    if (object.find(tmp.c_str()) != object.end())
    {
        std::wcout << tmp << std::endl;
        std::wcout.flush();
        initFromJSON(object[tmp.c_str()]->AsObject());
    }
    else
    {
        return false;
    }
}

Note that a std::wstring is returned, not a pointer. Then within the function itself, you use c_str() if you need to pass a const wchar_t*.

Upvotes: 1

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